Fluid motor



Malrch 5, 1963 w. -luNNlcUT-r 3,079,900.

FLUID MOTOR Filed June 26, 1961 IN VEN TOR.

Wayne HunncutiL BY l M9939 FLUB MGTR Wayne Huunicutt, Mukwenago, Wis., assigner to Applied Power lndustries, e., ltdliwaulsee, Wis., a corporation of Wisconsin Filed dune 2o, 196i, Ser. No. 119,591 9 Claims. (Cl. 121-164) The present invention relates generally to improvements in liuid motors, and relates more particularly to an improved pneumatically powered reciprocating piston type motor embodying automatically operable air servo means.

A primary object of the invention is to provide an improved fluid powered device which is extremely simple and compact in construction, highly efficient in operation, and ilexible in its adaptations.

Reciprocating piston type motors operable from an available source of pressurized air have many uses, one of which is to drive a hydraulic pump which, in turn, delivers high pressure hydraulic fluid to various tools as shown and described in the co-pending application of Neil F. Atherton and Joseph L. Johnston filed May 26, 1960, Serial No. 31,919. There are various prerequisites for such devices in order to render the same commercially acceptable, for example: they must be light and compact for portability and exibility in use; they must be capable of being readily produced at relatively low cost for assembly by unskilled labor; they must be durable and rugged to withstand the abuse to which they are subjected under various conditions; they must be elicient in operation and relatively insensitive to dust, liquid and other foreign matter as weil as to temperature changes frequently encountered during use; they must be readily manipulable and operable by means of convenient controls which are quickly and accurately responsive to the touch; and they must embody means for automatically supplying and exhausting pressurized lluid to and from the piston chamber in a proper manner for eicient operation.

It is accordingly a further object of my invention to provide an improved fluid motor which electively fulfills all of the above-mentioned requirements and which obviates the objections heretofore attendant devices of this same general type.

Another important object of this invention is to provide an improved air motor embodying a novel and automatically operable servo valve which is directly responsive to pressure conditions and the position of the piston within the displacement chamber as distinguished from prior arrangements wherein the valve serving the piston chamber is dependent upon the action of the throttle valve and the pressures existing in the air inlet line.

Still another object of the invention is to provide an improved air powered motor in which the air flow to and from the displacement chamber is automatically controlled independently of the throttle valve with utmost effectiveness and accuracy by a single extremely simple and unique poppet type valve, and a flow-limiting orifice so loc-ated as to furnish a trap for foreign matter which is easily cleaned without disassembly of the motor or valves.

A further important object of the present invention is to provide an improved motor of the reciprocating piston type operable by compressed air or other gaseous material and adapted to effectively operate over a wide range of airline pressure without adverse effect due to normal variations in the pressure within the supply line and Without requiring a separate pressure regulator.

These and other objects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying tates liars a drawing wherein like reference characters designate the same or similar parts in the several views.

FIG. l is a fragmentary longitudinal section through an air powered motor embodying the invention, the section being taken along a line extending longitudinally through the breather passage connecting the forward end of the displacement chamber to exhaust and showing the piston in starting position;

FIG. 2 is another longitudinal section through the device but taken along a line extending longitudinally through the by-pass connecting the displacement chamber with the servo chamber and showing the piston in its forward position; and

FIG. 3 is a somewhat reduced end transverse section through the unit taken along the line 3-3 of FIG. 2.

While reference has been made herein to the fact that the improved fluid motor is operable by compressed air obtained from -a suitable source and is especially adapted for use in combination with and for the purpose of actuating a hydraulic pump for developing high pressures, it is not intended to thereby unnecessarily restrict the operation or utility of the -device by reason of such limited embodiments; and it is also contemplated that certain speciic descriptive terms used herein shall be given the broadest possible interpretation consistent with the dis closure.

Referring to the drawing, the iuid motor shown therein as embodying the invention comprises, in general, a hollow cylindrical body 5 having end closures 6, 7 and forming a displacement chamber S for a piston 9. The piston 9 is provided with a suitable sealing ring or packing it), shown as a rubber O-ring, coniined in an annular groove 11 and sealingly but slidably ccacting with the inner wall of the chamber 8, and the piston is constantly resiliently urged toward one end of the chamber 8 by a compression spring i2 seated between the end closure 7 and the Iadjacent face of the piston 9. A shaft or rod 13 extending through a central apertureA 14 in the end closure 7 and between the coils of the Vspring i2 cooperates With an annular cup-shaped plate l5 `within which one end of the spring is seated to retain the spring l2 in position and prevent displacement thereof. For ease oi' assemblyV and to avoid the need for close tolerances in manufacture, the inner end of the rod 13 is provided with an annular ange or head 16 which prevents endwise displacement of the plate 15 and which is loosely seated against the convex bottom surface of a central recess or pocket 17 formed in the front face of the piston 9, and the rod i3 may be suitably connected to perform the desired work or it may, of itself, constitute the hydraulic pump plunger as in the co-pending application above-identified.

The end closure 6 contains the air inlet port 19, throttle valve 2t), poppet type servo valve 21, servo chamber 2-2 and exhaust port 23. The inlet port 19 is in open communication with ya suitable source of compressed `air, not shown, via a flexible hose or air line 24 having the usual threaded coupling 25' for attaching the line 2.4 to the end closure 6, the port 19 in turn communicating with the adjacent end of the motor chamber 8 past-a 'call check valve 26 normally seated against an annular ring or gasket 27, preferably formed of resilient sealing material, by the action of a compression spring 2.3. The throttle valve 2) for ladmittirng pressurized air from the inlet port 19 to the chamber S comprises a threaded plug or bushing 29 slidably ,receiving the valve actuating stem 3b which has a suitable O-ring seal 31 or the like slidably but sealingly coacting with the bushing, the stern Sli having an outwardly projecting portion Stl adapted to be depressed to thereby cause the inner end or the stem to unseat the ball 26 in oppositionv to the spring 2d' andaair pressure in cham.-

ber 19. The inner end of the bushing or plug 29 immediately above the valve seat 27 is provided with radial ports 32 communicating on one side with the air inlet port 19 past the ballvvalve 26 and on-the other side directly with a recess formed on the inner face of the end closure 6 and opening to the adjacent end of the motor chamber 8. Thus, when the stem 30 of the throttle valve l20 is depressed to unseat the ball 26, live air is admitted from the inlet port 19 through a reduced orifice 34 past the ball 26 and through the ports 32 in the plug 29 to the recess 33 and chamber 8 where it acts on the rear face of the piston 9 to move the same toward the opposite end of theV motor chamber in opposition to the spring 12.

To permit entrapped air to escape from the forward end of the chamber 8 as the piston 9 is thus moved, a port 36 is formed in the Wall of the cylinder 5, and the base plate 37, which may also form a stand for the air motor, is provided with a longitudinal recess or channel 38 communicating at one end with this port 36 and its opposite end with the exhaust port 23 through a radial passage 39 in the'end closure 6. The base plate or stand 37 may be stamped from sheet metal stock or may be machined from a casting, bar or the like and is suitably `attached to the Vmotor body as by means of machine screws 40 threaded to the end closures 6, 7 with a rubber gasket 41 being positioned therebetween. During this forward advancement of the piston 9 by live air admitted from the inlet port 19 to the chamber 8 at the rear of the piston 9,'there' are no unbalanced pressures acting on the poppet type valve 21 which would tend to unseat the same,'the valve 21 being formed with a reduced stem portion 42 intermediate its ends which affords direct communication between the adjacent slurounding space and the exhaust port 23.

" However, as the motor piston 9 reaches the end of its forward stroke, a port 44 also formed inthe Wall of the cylinder at an intermediate portion of the chamber 8 operative position and a motor piston having a diameter of 2.630 inches with exhaust porting totaling .230 square inch of area, an inlet or supply orifice having a diameter of .078 inch is found to give the desired results, and any increase in the area of the exhaust porting will increaseY the cyclic rate of the motor piston. Of course, various factors other than return spring force, motor piston area and area of the exhaust porting may have some effect on the correct orifice size, including piston friction, vresi-stance to the return stroke and leakages, but the size of the inlet orifice may be readily adjusted for the desired operation. Also, the area of the rear face or servo portion 47 of the automatically operable free-sliding valve 21 must be somewhat larger than the exhaust sealing face of the valve as seated at 49 -in order to actuate the valve against the pressure existing in the rear of the chamber 8.

From the foregoing detailed description, it is believed apparent that the present invention contemplates the provision of a simple and compact air motor which comprises 1 which requires little maintenance Also,

is uncovered, and this port 44 establishes communication between the chamber 8, rearwardly of the piston 9 when in lits forward position, and the servo chamber 22 via a longitudinal passageway 45 formed inthe gasket 41 and a radial passage 46 formed in the end closure 6. Thus, as

the piston 9 uncovers the port 44, the pressurized air being admitted to the chamber 8 rearwardly of the piston is by-passedthrough the port 44, passageway and passage A46 to the servo chamber 22 behind the large diameter servo portion or 'rear face 47 of the valve 21, and the pressure build-up in the servo chamber unbalances the valve 21 and unseats the same to thereby permit live air t0., escape directly from the adjacent end of the chamber A8 and recess 33 to the exhaust port 23 past the reduced stem portion 42 of the valve.

Thus, since the air is permitted to escape from the rear of the piston 9 directly to exhaust, the compression spring 12 becomes active to return the motor piston 9 4to itsV starting position, and as the piston is moved rearwardly in the chamber 8 by the spring 12, its rear facev contacts the extending nose portion 48 of the poppet v valve 21 and forces the valve against its seat 49. With the valve 21 again seated, the chamber 8 to the rear of the piston is shut ol from the exhaust port, and another operating cycle is begun, the above-described action being continuously automatically repeated until such time as the stem of the throttlevalve 30 is released.

VIn order to limit the mass liow rate of pressurized supply air to the rear end of the chamber 8 and thereby allow operation of the device over a wide range of airline pressures with minimum air volume consumption, the orifice 34 should be sized relative to the volume of the chamber 8, net area of the exhaust port or ports 23 and force of the spring 12 for returning the piston 9 to its starting position. As a specific example in a device adapted to operate effectively at airline pressures ranging from 5 p.s.i. to 200 p.s.i., and embodying a piston return spring exerting a force of l4pounds when initszstatic ina minimum number of parts capable of being readily produced and assembled at relatively low cost and by unskilled labor. The ow of pressurized air is effectively automatically controlled by a unique poppet type valveV j and the operation of which is unaliected by temperature and other operating conditions, and the cycling operation automatically continues without interruption as long as the throttle valve is not released. As shown in FIG. 3 of the drawing', the

v* recess in the valve block 6 opening into the adjacent'end Y of the piston chamber 8 is preferably formed by an annular series of bores which peripheraly intersect the valve seat 49 to thus provide an annular series of spaced guide surfaces 51 for the valve 21 in its reciprocating movement.v to obtain access to the poppet valve conveniently, the valve block 6 is formed with a rear opening which is closed by a threaded closure plug 52, and access to the poppet valve may be readily obtained for purposes of periodic inspection or cleaning merely by removal of this plug 52 in an obvious manner. Devices embodying the invention have moreover proven extremely efficient and durable in actual use, and the simplicity of the controls permit a wide iiexibility of adaptation.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim: i

Il. A iluid motor comprising, a body having a piston chamber formed therein, a piston reciprocable with-in said chamber, a valve block closing an end of said chamber, a fluid pressure supply passageway in said valve block communicable with the adjacent end of said chamber, a throttle valve normally closing said supply passageway and operable to open the same and establish direct communication between said supply passageway and said chamber, means forming an exhaust passage in said valve block communicable with opposite ends of said chamber, a freely reciprocable valve in said valve block operable when seated to close said chamber from said exhaust .passage and when unseated to establish direct communication between said chamber and said exhaust passage, said piston being moved in one direction by iiuid pressure admitted to said chamber when said valve is seated, another passageway communicable with an intermediate portion of said chamber and one end of said freely reciprocable valve dependent upon the position of said piston in said chamber for conducting pressurized uid from said chamber to said valve end to unseat said valve and thereby open said chamber to said exhaust passage, and means for moving said piston in the opposite direction when said valve is unseated. 2. A fluid motor accord-ing to claim 1, wherein the freely reciprocable ,valve is of poppet type having an intergn'ediateportion of reducedA diameter to vpermit the establishment of direct communication between the chamber and the exhaust passage when said valve is unseated.

3. A iiuid motor according to claim 2, wherein the opposite ends of the valve are of different areas with the end upon which the pressurized fluid acts to unseat the valve being of greater area than the end which controls ow from the chamber to exhaust.

4. A uid motor according to claim 1, wherein the uid pressure supply passageway has an orifice therein of reduced size to limit the mass flow rate of air supplied to the chamber.

5. A fluid motor according to claim 1, wherein the uid pressure supply passageway opens into a recess formed in the valve block at the adjacent end of the chamber and in direct open communication therewith.

6. A fluid motor according to claim l, wherein the freely reciprocable valve is formed with a portion extending into the chamber and directly engageable by the piston when moved in said opposite direction to thereby seat said valve.

7. A uid motor comprising, a body having a piston chamber formed therein, a piston reciprocable within said chamber, a valve block closing an end of said chamber, a duid pressure supply passageway in said valve block communicable with the adjacent end of said chamber, a throttle valve normally closing said supply passageway and operable to open the same and establish direct communication between said supply passageway and said chamber, means forming an exhaust passage in said valve block communicable with opposite ends of said chamber, a freely reciprocable valve spool in said valve block having one end thereof operable when seated to close said chamber from said exhaust passage and when unseated to establish direct communication between said chamber and said exhaust passage through the intermediate portion oi' said valve, said piston being moved in one direction by duid pressure admitted to said chamber when said valve is seated, another passageway communicable with an intermediate portion of said chamber and the other end of said freely reciprocable valve dependent upon movement of said piston in said one direction for conducting pressurized uid from said chamber to the other end of said valve to unseat said one end thereof and thereby open said chamber to said exhaust passage, and spring means for moving said piston in the reverse direction when said valve is unseated.

8. A iiuid motor according to claim 7, wherein said other end of the freely reciprocable valve is of greater diameter than the diameter of said one end thereof.

9. A iiuid motor according to claim 8, wherein said one end of the freely reciprocable valve has an integral nose projecting into the chamber and directly engageable by the piston when moved in said reverse direction to seat said valve.

References Cited in the file of this patent UNITED STATES PATENTS 1,971,048 Parsons Aug. 21, 1934 FOREEGN PATENTS 764,509 France Mar. 5, 1934 

1. A FLUID MOTOR COMPRISING, A BODY HAVING A PISTON CHAMBER FORMED THEREIN, A PISTON RECIPROCABLE WITHIN SAID CHAMBER, A VALVE BLOCK CLOSING AN END OF SAID CHAMBER, A FLUID PRESSURE SUPPLY PASSAGEWAY IN SAID VALVE BLOCK COMMUNICABLE WITH THE ADJACENT END OF SAID CHAMBER, A THROTTLE VALVE NORMALLY CLOSING SAID SUPPLY PASSAGEWAY AND OPERABLE TO OPEN THE SAME AND ESTABLISH DIRECT COMMUNICATION BETWEEN SAID SUPPLY PASSAGEWAY AND SAID CHAMBER, MEANS FORMING AN EXHAUST PASSAGE IN SAID VALVE BLOCK COMMUNICABLE WITH OPPOSITE ENDS OF SAID CHAMBER, A FREELY RECIPROCABLE VALVE IN SAID VALVE BLOCK OPERABLE WHEN SEATED TO CLOSE SAID CHAMBER FROM SAID EXHAUST PASSAGE AND WHEN UNSEATED TO ESTABLISH DIRECT COMMUNICATION BETWEEN SAID CHAMBER AND SAID EXHAUST PASSAGE, SAID PISTON BEING MOVED IN ONE DIRECTION BY FLUID PRESSURE ADMITTED TO SAID CHAMBER WHEN SAID VALVE IS SEATED, ANOTHER PASSAGEWAY COMMUNICABLE WITH AN INTERMEDIATE PORTION OF SAID CHAMBER AND ONE END OF SAID FREELY RECIPROCABLE VALVE DEPENDENT UPON THE POSITION OF SAID PISTON IN SAID CHAMBER FOR CONDUCTING PRESSURIZED FLUID FROM SAID CHAMBER TO SAID VALVE END TO UNSEAT SAID VALVE AND THEREBY OPEN SAID CHAMBER TO SAID EXHAUST PASSAGE, AND MEANS FOR MOVING SAID PISTON IN THE OPPOSITE DIRECTION WHEN SAID VALVE IS UNSEATED. 